Some of the popular RTL2832U based DVB-T dongles that can be used as SDR tend to heat too much. As temperature increases, frequency drifts and sensitivity drops. Some dongles, especially those using R820T may stop working at all at high temperatures.

Although I'm using a R820T2 dongle (which is said to heat less than the predecessor R820T), I was surprised to see that after only 10-15 minutes the dongle was hot. Opening it up, I discovered that all ICs were hot (the tuner R820T2, the RTL2832U, the 1117 regulator, even the EEPROM was heated inside the closed case of the dongle).